1. Field of the Invention
The present invention concerns a method for three-dimensional measurement of objects, and in particular large objects, and a three-dimensional measuring device including mobile measuring means which at no time come into contact with the objects to be measured.
2. Description of the Prior Art
The prior art comprises many three-dimensional measuring machines. A swan-neck type machine is conventionally used in metrology, for example. This type of machine offers good measurement accuracy, but is restricted to measuring objects of small size and weight, typically less than one meter and 100 kilograms. A gantry (boom or bridge) type machine is suitable for large objects but is not so accurate, because of the heterogeneous nature of its construction and the number of moving parts that it includes.
For large objects, for example objects from five to ten meters long, the prior art teaches the use of an intersection measurement system including two theodolites which can be moved around the object to be measured, for example. Each time that the theodolites are moved and positioned, the orientation of each theodolite has to be determined relative to the other theodolite and relative to a fixed system of axes. The measurements are then carried out point by point. The accuracy of the measurements produced by an intersection measurement system is in the same order of magnitude as that of a swan-neck type three-dimensional measuring machine. However, the use of two theodolites is difficult and it takes a long time to measure an object.